1. Technical Field of the Invention
The present invention relates to a structural member having a generally U-shaped cross-section and a longitudinally extending configuration, comprising a base portion and two leg portions extending at substantially right angles from said base portion.
Such structural members are used in a wide field of applications, and their structure and material vary according to the demands made by the particular field.
2. Prior Art
For instance, international published application No. WO 90/03921 discloses a support member for pallets, comprising a channel having a generally U-shaped cross-section. The support member is manufactured from flat sheets of metal, such as steel or aluminum. In order to increase the stiffness of the support member, ribs are pressed into the base and side panels at regular intervals along the length of the support member. The support member disclosed in this document presents good load-bearing properties combined with a relatively low weight.
In other fields of application, it is not only the load-bearing capacity which is important. In order to avoid dimensional stability problems in thin-walled structures such as shell-shaped tools or moulds, or other structures such as boat hulls or aircraft parts, it is well known to provide such structures with reinforcing or stiffening elements. These elements may comprise eg. steel pipes or bars, or profiles having any cross-section, of which rather short parts are welded together in order to adjust the reinforcing or stiffening elements to the shape of structure which may often have a non-planar surface, eg. a surface of double curvature.
From the field of moulding plastic or composite materials, it is known to provide the backside of the tool or mould face with a reinforcing stiffener in the form of a flexible spiral square tube of fibre glass or graphite cloth which is conformed to the shape of the shell to be reinforced and subsequently covered by a mat of glass fibre and subjected to autoclave treatment. However, the flexible tube is relatively expensive and difficult to handle.
It is the object of the invention to provide an alternative to the prior art elements described in the above.
To achieve this, the structural member according to the invention is characterized in that said structural member comprises at least one thin sheet or foil which is corrugated in a continuous waveform in the longitudinal direction of the member; and that each leg portion includes a first section forming an inner wall of the leg portion and a second section parallel with said first section and joining the first section along a first joining line and the base portion along a second joining line.